Tile Calculator — How Many Tiles Do I Need?

Your Tile Project Guide

Whether you're retiling a bathroom floor, installing a kitchen backsplash, or laying new flooring in an entryway, knowing exactly how many tiles you need saves money and avoids frustrating delays. This tile calculator factors in your room dimensions, tile size, grout spacing, and waste percentage to give you an accurate count — including how many boxes to buy.

The waste percentage is one of the most important inputs, and beginners often underestimate it. For a simple grid layout in a rectangular room, 10% waste covers cuts along the edges, the occasional broken tile, and a few extras for future repairs. If you're doing a diagonal pattern, herringbone, or any layout that requires angled cuts, bump that up to 15%. Complex room shapes with lots of corners, alcoves, or curves may need 20%.

Grout spacing also affects your total tile count, though the impact is small. The standard 1/8-inch grout joint for rectified (precisely cut) tiles means each tile plus its grout effectively covers a slightly larger area. Larger format tiles (18x18 or bigger) typically use 3/16-inch grout lines. Make sure to match your grout joint width with the tile manufacturer's recommendation — some tiles aren't suitable for tight grout lines.

Before ordering, double-check that all your boxes come from the same production lot. Tile color can vary slightly between manufacturing batches, and mixing lots can create visible differences once installed. Order everything at once, and hold onto at least a few extra tiles for future repairs — matching discontinued tile years later is nearly impossible.

Tile installation on a floor requires a solid, flat substrate. On concrete, you can typically tile directly after cleaning and leveling. On wood subfloors, you'll want 1/4-inch cement backer board screwed down to prevent flexing that cracks grout lines. The thinset mortar you use matters too — large format tiles (anything over 15 inches on a side) need a medium-bed mortar and should be back-buttered for full coverage.

For backsplashes, the math is the same but the area is smaller — measure the width and height of the area between your countertop and upper cabinets. Subway tile (3x6 inches) remains the most popular backsplash choice because it's affordable, timeless, and relatively easy to install.